Mobile computing devices have been developed to increase the functionality that is made available to users in a mobile setting. For example, a user may interact with a mobile phone, tablet computer, or other mobile computing device to check email, surf the web, compose texts, interact with applications, and so on. Modern mobile computing devices may incorporate multiple antennas to support various wireless subsystems and communications. The multiple antennas may include for example one or more Wi-Fi, Bluetooth, global navigation satellite system (GNSS), near field communication (NFC) and/or cellular antennas.
One challenge faced by mobile computing device designers is adherence to regulatory requirements that are imposed by entities such as the Federal Communication Commission (FCC), the European Union (EU), and so forth. An example of such regulatory requirements is legal limits on Specific Absorption Rate (SAR) that are established in relation to radio frequency (RF) energy associated with the various wireless and communications subsystems of a mobile computing device. A traditional solution for achieving compliance with SAR limits involves setting a fixed maximum RF transmit power for communication hardware (e.g., radios) to a power level that maintains legal compliance in the presence of a user. However, placing such a fixed maximum on the transmit power underutilizes the capabilities of communication hardware and may adversely affect communication connections and/or quality. Additionally, add-on hardware and/or accessory devices connectable to a host device may have adverse influences upon RF emissions of the host device that typically are not accounted for in traditional mitigation approaches. Thus, traditional techniques for SAR compliance may be inadequate for some device configurations and use scenarios.